Optical and electrical interconnect

ABSTRACT

An interconnect comprising an anisotropic conductive film and an optically transmissive unit embedded in the anisotropic conductive film. The optically transmissive unit provides an optically transmissive path through the anisotropic conductive film. In an alternative embodiment, an electronic package comprises a first substrate, a second substrate, and an interconnect located between the first substrate and the second substrate. The interconnect comprises an anisotropic conductive film for electrically coupling a first conductive element formed on the first substrate to a second conductive element formed on the second substrate and one or more optically transmissive units embedded in the anisotropic conductive film. At least one of the one or more optically transmissive units couples an optical signal path on the first substrate to an optical receiver on the second substrate.

FIELD

[0001] The present invention is related to connecting signals betweensubstrates in an electronic package and, more particularly, tointerconnects used in connecting electronic and optical signals betweensubstrates in an electronic package.

BACKGROUND

[0002] Electrical interconnects are conductive structures that carrysignals and information in modem electronic systems, such as computers,cellular telephones, and personal digital assistants. Substrates,including dice and packaging substrates, are the building blocks ofmodem electronic systems. Dice are electronic components made up ofdiodes, transistors, resistors, capacitors, and inductors that performthe electronic functions required in modem electronic systems. Packagingsubstrates provide a platform for mounting and interconnecting dice andother electronic components, such as resistors, capacitors, andinductors. Electrical interconnects connect together electroniccomponents on and between dice and packaging substrates.

[0003] Electrical interconnects are a significant informationtransmission bottleneck in modern communication and computation systems.Information encoded in electronic signals is transmitted betweenelectronic components over electrical interconnects in modemcommunication and computation systems. Electrical interconnects areoften unable to transfer information at the high data rates that modemsystems require. One reason for this is that electrical interconnectsare often fabricated from conductive materials, such as metals, whichhave several inherent electrical limitations. First, electricalinterconnects are susceptible to noise pick-up from neighboringconductors. Second, electrical interconnects have a finite resistancewhich when coupled to parasitic capacitances limits the speed at whichinformation can be transmitted on the interconnects.

[0004] For these and other reasons there is a need for the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005]FIG. 1A is a perspective view of one embodiment of an interconnectaccording to the teachings of the present invention;

[0006]FIG. 1B is a side view of the interconnect shown in FIG. 1A;

[0007]FIG. 1C is magnified view of a section of the anisotropic film ofthe interconnect shown in FIG. 1B;

[0008]FIG. 1D shows a section of the anisotropic film of theinterconnect shown in FIG. 1C after compression;

[0009]FIG. 1E is a exploded view of one embodiment of an interconnectlocated between a first substrate and a second substrate according tothe teachings of the present invention;

[0010]FIG. 1F is a cross-sectional view of the interconnect locatedbetween the first substrate and the second substrate of FIG. 1E takenalong the line A-A; and

[0011]FIG. 2 is a flow diagram of one embodiment of a method offabricating an interconnect according to the teachings of the presentinvention.

DESCRIPTION

[0012] In the following detailed description of the invention, referenceis made to the accompanying drawings which form a part hereof, and inwhich are shown, by way of illustration, specific embodiments of theinvention which may be practiced. In the drawings, like numeralsdescribe substantially similar components throughout the several views.These embodiments are described in sufficient detail to enable thoseskilled in the art to practice the invention. Other embodiments may beutilized and structural, logical, and electrical changes may be madewithout departing from the scope of the present invention. The followingdetailed description is not to be taken in a limiting sense, and thescope of the present invention is defined only by the appended claims,along with the full scope of equivalents to which such claims areentitled.

[0013]FIG. 1A is a perspective view of one embodiment of an interconnect100 according to the teachings of the present invention. Theinterconnect 100 includes an anisotropic conductive film 102 andoptically transmissive units 104-106 embedded in the anisotropicconductive film 102.

[0014]FIG. 1B is a side-view of the interconnect 100 shown in FIG. 1A.The side-view is taken at surface 109 of the interconnect 100 shown inFIG. 1A. As can be seen in FIG. 1B, each of the optically transmissiveunits 104-106 provides an optically transmissive path through theanisotropic conductive film 102. Thus, each of the opticallytransmissive units 104-106 provides a path for coupling optical signalsfrom the first surface 108 of the interconnect 100 to the second surface110 of the interconnect 100 and from the second surface 110 of theinterconnect 100 to the first surface 108 of the interconnect 100.

[0015] The interconnect 100, in the embodiment shown in FIG. 1A and FIG.1B, includes three optically transmissive units 104-106. However, theinterconnect 100 is not limited to use in connection with threeoptically transmissive units. The interconnect 100 can be fabricatedwith as many or as few optically transmissive units as a particularapplication requires. In the embodiment shown in FIG. 1A, theinterconnect 100 has a first surface 108 that is substantiallyrectangular. However, the first surface 108 of the interconnect 100 isnot limited to a substantially rectangular shape. The first surface 108can be formed to any shape that a particular application requires.

[0016] Optically transmissive units 104 and 106, in one embodiment asshown in FIG. 1A, have a substantially cylindrical shape. Opticallytransmissive unit 105, in one embodiment as shown in FIG. 1A, has asubstantially rectangular shape. However, the optically transmissiveunits 104-106 are not limited to a particular shape. Any shape that iscapable of transmitting optical energy is suitable for use in thefabrication of optically transmissive units 104-106. Thus, the opticallytransmissive units 104-106 can be shaped to efficiently transmitelectromagnetic radiation from a variety of sources, including diemounted (not shown) lasers, such as vertical cavity surface emittinglasers, laser diodes, and diodes, and externally mounted (not shown)lasers, laser diodes, and diodes.

[0017] Optically transmissive units 104-106 are not limited to beingfabricated using a particular material. In one embodiment, opticallytransmissive units 104-106 comprise free space. In an alternativeembodiment, optically transmissive units 104-106 are fabricated from anoptical polymer. Exemplary optical polymers suitable for use inconnection with the fabrication of optically transmissive units 104-106include acrylic acrylates, polycarbonates, or polyacrylates. Preferably,the optical polymers selected for the fabrication of the opticallytransmissive units 104-106 are curable using ultraviolet radiation.

[0018] The optically transmissive units 104-106 can function as opticalvias in modem electronic systems. A via is an interconnection forcoupling together components in electronic systems. A via can coupletogether components on a single substrate or components on multiplesubstrates. Vias in modern electronic systems are generally conductiveelements. However, optically transmissive units 104-106 can alsofunction as vias to couple optical signals between components in anelectronic system. Those skilled in the art will appreciate that the useof optically transmissive units 104-106 as vias in an electronic systemcan increase the bandwidth of the system.

[0019]FIG. 1C is a magnified view of section 111 of the anisotropicconductive film 102 of the interconnect 100 shown in FIG. 1B. As can beseen in FIG. 1C, the section 111 of the anisotropic conductive film 102includes a carrier 112 and one or more conductive particles 114 embeddedin the carrier 112. In one embodiment, the carrier 112 is asubstantially compliant insulative material. Exemplary substantiallycompliant insulative materials include epoxies and adhesives.

[0020] In one embodiment, each of the one or more conductive particles114 is fabricated from a conductive material. Exemplary conductivematerials suitable for use in the fabrication of the one or moreconductive particles 114 include metals and semiconductors. Exemplarymetals suitable for use in the fabrication of the one or more conductiveparticles 114 include nickel, aluminum, copper, gold, silver, and alloysof nickel, aluminum, copper, gold and silver. Exemplary semiconductorssuitable for use in the fabrication of the one or more conductiveparticles 114 include silicon, germanium, and gallium arsenide.

[0021]FIG. 1D shows the section 111 of the anisotropic conductive filmof FIG. 1C after compression. As can be seen in FIG. 1D, aftercompression of the anisotropic film 102 at a point of compression 116, aconductive path 118 is formed between the point of compression 116 andthe second surface 110 by a subset of the one or more conductiveparticles 114. The density of the one or more conductive particles 114in the carrier 112 and the compliancy of the carrier 112 are selectedsuch that, with the carrier compressed as shown in FIG. 1D, a subset ofthe one or more conductive particles 114 forms the conductive path 118between the first surface 108 at the point of compression 116 and thesecond surface 110. The point of compression 116 is the location on thefirst surface 108 at which an electrical connection can be made to theconductive path 118.

[0022]FIG. 1E is a perspective view of one embodiment of an electronicpackage 119 according to the teachings of the present invention. Theelectronic package 119 includes interconnect 100 located between a firstsubstrate 120 and a second substrate 122. In one embodiment, the firstsubstrate 120 comprises a die including electrical optical circuits (notshown), and the second substrate 122 comprises a carrier substrateincluding electrical and optical signal carrying paths (not shown).However, the first substrate 120 is not limited to a particular type ofdie, and the second substrate 122 is not limited to a particular type ofcarrier substrate. Exemplary dice suitable for use in connection withthe present invention include microprocessor, digital signal processor,or application specific integrated circuit dice. Exemplary substratessuitable for use in connection with the present invention includesingle-die ceramic carriers and multi-die ceramic carriers. After thefirst substrate 120, the second substrate 122, and the interconnect 100are assembled into the electronic package 119, the interconnect 100provides electrical and optical signal paths (not shown) fortransmitting electrical and optical signals between the first substrate120 and the second substrate 122 and between the second substrate 122and the first substrate 120. Those skilled in the art will appreciatethat FIG. 1E shows only one embodiment of the electronic package 119,and that the electronic package 119 is not limited to being fabricatedusing only two substrates as shown in FIG. 1E. Three or more substratescan be optically and electrically coupled together using the teachingsof the present invention. In one embodiment, a die substrate iselectrically and optically coupled to a ceramic substrate, and theceramic substrate is electrically and optically coupled to a motherboardsubstrate.

[0023]FIG. 1F is a cross-sectional view of the electronic package 119shown in FIG. 1E taken along the line A-A. The electronic package 119includes the first substrate 120, the second substrate 122, and theinterconnect 100 located between the first substrate 120 and the secondsubstrate 122. The first substrate 120 includes optical paths 127-128,optical transmitter 130, optical receivers 132-133, terminals or diepads 136-139, and conductive solder elements 141-144. The interconnect100 includes optically transmissive units 104-106, conductive paths145-148, and anisotropic conductive film 102. The second substrate 122includes optical paths 150-153, reflectors 156-159, and electricallyconductive terminals or pads/lands 161-164. Each of the optical pathsincludes one of the reflectors 156-159 for deflecting an optical beam.

[0024] As can be seen in FIG. 1F, the interconnect 100 is compressed atconductive solder elements 141-144 to form the electrically conductivepaths 145-148 between each of the conductive solder elements 141-144 onthe first substrate 120 and the electrically conductive terminals orpads/lands 161-164 on the second substrate 122. Thus, each of theelectrically conductive paths 145-148 provides a path for coupling anelectrical signal from the first substrate 120 to the second substrate122 and from the second substrate 122 to the first substrate 120. Also,as can be seen in FIG. 1F, the interconnect 100 provides optical pathsat optically transmissive units 104-106 for coupling optical signalsbetween the first substrate 120 and the second substrate 122. Thesources of optical signals 166-168 are not shown in FIG. 1F, howeverthose skilled in the art will appreciate that exemplary sources ofoptical signals 166-168 include but are not limited to lasers, verticalcavity surface emitting lasers, diodes, and laser diodes. Those skilledin the art will also appreciate that optical signals can be coupled tooptical input ports 170-172.

[0025] In operation, the second substrate 122 receives the opticalsignals 166-168 at optical input ports 170-172, respectively, and thefirst substrate 120 transmits optical signal 174 from opticaltransmitter 130 to optical output port 176 on the second substrate 122.In addition, electrical signals, such as digital or analog signals, aretransmitted between the first substrate 120 and the second substrate122. The electrical signals transmitted between the first substrate 120and the second substrate 122 traverse paths that include the terminalsor die pads 136-139, the conductive solder elements 141-144, theconductive paths 145-148, and the terminals or pads/lands 161-164.

[0026] The optical signal 166, after arriving at the optical input port170, travels along the optical path 151 to the reflector 157. At thereflector 157, the optical signal 166 is deflected into the opticallytransmissive unit 105. The optical signal 166 travels through theoptically transmissive unit 105 to the optical receiver 132 on the firstsubstrate 120. The optical receiver 132 receives and processes theoptical signal 166 or receives and converts the optical signal 166 to anelectrical signal for further processing.

[0027] The optical signal 167, after arriving at the optical input port171, travels along the optical path 152 to the reflector 158. At thereflector 158 the optical signal 167 is deflected into the opticallytransmissive unit 105. The optical signal 167 travels through opticallytransmissive unit 105 to the optical path 128 on the first substrate120. The optical signal 167 travels along optical path 128 to theoptical receiver 132 on the first substrate 120. The optical receiver132 receives and processes the optical signal 167 or receives andconverts the optical signal 167 to an electrical signal for furtherprocessing. The optical receiver 132, in one embodiment, comprises asingle optical receiver. In an alternative embodiment, the opticalreceiver 132 comprises a plurality of optical receivers.

[0028] Thus, optical signals 166 and 167 are both transmitted throughthe optically transmissive unit 105. Those skilled in the art willappreciate that each of the optically transmissive units 104-106 canroute a plurality of optical signals between the first substrate 120 andthe second substrate 122.

[0029] The optical signal 168, after arriving at the optical input port172, travels along the optical path 153 to the reflector 159. At thereflector 159 the optical signal 168 is deflected into the opticallytransmissive unit 106. The optical signal 168 travels through theoptically transmissive unit 106 to the optical receiver 133 on the firstsubstrate 120. The optical receiver 133 receives the optical signal 168and processes the optical signal 168 or converts optical signal 168 toan electrical signal for further processing. The optical receiver 133,in one embodiment, comprises a single optical receiver. In analternative embodiment, the optical receiver 133 comprises a pluralityof optical receivers.

[0030] The optical transmitter 130 generates an optical signal 174 onthe first substrate 120. The optical signal 174 travels along theoptical path 127 to the optically transmissive unit 104. The opticalsignal 174 travels through the optically transmissive unit 104 and tothe optical path 150 on the second substrate 122. The optical signal 174travels along the optical path 150 to the reflector 156 and is deflectedalong the optical path 150 to the optical output port 176.

[0031] Thus, the interconnect 100 provides an interconnect that permitstransmission of optical and electrical signals from the first substrate120 to the second substrate 122 and from the second substrate 122 to thefirst substrate 120.

[0032] Those skilled in the art will appreciate that the optical signalspassing through the optically transmissive units 104-106 aresubstantially immune from electrical interference, such as cross-talkfrom electrical signals passing through the conductive paths 145-148. Inaddition, the optical signals passing through the optically transmissiveunits 104-106 do not interfere with the electrical signals beingtransmitted through the electrically conductive paths 145-148. In oneembodiment, the signal passing through the at least one of the opticallytransmissive units 104-106 is a clock signal.

[0033] Those skilled in the art will also appreciate that opticalsignals passing through the optically transmissive units 104-106 areimmune from parasitic capacitances, which allows signals to betransmitted through the optically transmissive units 104-106 at higherfrequencies than signals transmitted on the electrically conductivepaths 145-148.

[0034]FIG. 2 is a flow diagram of one embodiment of a method 200 offabricating an interconnect according to the teachings of the presentinvention. Method 200 includes forming one or more holes in a conductivefilm on a carrier substrate (block 201), filling at least one of the oneor more holes with a material capable of transmitting an optical signal(block 203), and laminating the conductive film on a packaging substrate(block 205). In an alternative embodiment, forming one or more holes inthe conductive film comprises patterning the conductive film to form apatterned conductive film and etching the one or more holes in thepatterned conductive film. In another alternative embodiment, filling atleast one of the one or more holes with a material capable oftransmitting an optical signal comprises filling at least one of the oneor more holes with an optical polymer.

[0035] Although specific embodiments have been described and illustratedherein, it will be appreciated by those skilled in the art, having thebenefit of the present disclosure, that any arrangement which isintended to achieve the same purpose may be substituted for a specificembodiment shown. This application is intended to cover any adaptationsor variations of the present invention. Therefore, it is intended thatthis invention be limited only by the claims and the equivalentsthereof.

What is claimed is:
 1. An interconnect comprising: an anisotropicconductive film; and an optically transmissive unit embedded in theanisotropic conductive film, the optically transmissive unit providingan optically transmissive path through the anisotropic conductive film.2. The interconnect of claim 1, wherein the anisotropic conductive filmcomprises an adhesive, anisotropic conductive film.
 3. The interconnectof claim 2, wherein the adhesive, anisotropic conductive film comprisesan epoxy and a plurality of conductive particles embedded in the epoxy.4. The interconnect of claim 3, wherein the optically transmissive unitoptically couples each of a plurality of optical transmitters to one ormore optical receivers.
 5. The interconnect of claim 1, wherein theoptically transmissive unit optically couples each of a plurality ofoptical transmitters to one or more optical receivers.
 6. Theinterconnect of claim 5, wherein the optically transmissive unit has atransmission area that is substantially rectangular .
 7. Theinterconnect of claim 5, wherein the anisotropic conductive filmcomprises an adhesive, anisotropic conductive film.
 8. The interconnectof claim 1, wherein the optically transmissive unit comprises an opticalpolymer.
 9. The interconnect of claim 8, wherein the optical polymercomprises an acrylic acrylate.
 10. The interconnect of claim 9, whereinthe optically transmissive unit comprises a substantially cylindricaloptically transmissive material.
 11. A method of fabricating aninterconnect, the method comprising: forming one or more holes in ananisotropic conductive film on a carrier substrate; filling at least oneof the one or more holes with a material capable of transmitting anoptical signal; and laminating the anisotropic conductive film on apackaging substrate.
 12. The method of claim 11, wherein forming one ormore holes in the anisotropic conductive film comprises: patterning theanisotropic conductive film to form a patterned anisotropic conductivefilm; and etching the one or more holes in the patterned anisotropicconductive film.
 13. The method of claim 11, wherein filling at leastone of the one or more holes with a material capable of transmitting anoptical signal comprises filling at least one of the one or more holeswith an optical polymer.
 14. An electronic package comprising: a firstsubstrate; a second substrate; and an interconnect located between thefirst substrate and the second substrate, the interconnect comprising: aconductive film for electrically coupling a first terminal formed on thefirst substrate to a second terminal formed on the second substrate; andone or more optically transmissive units embedded in the conductivefilm, wherein at least one of the one or more optically transmissiveunits provides an optical signal path between an optical element on thefirst substrate and an optical element on the second substrate.
 15. Theelectronic package of claim 14, wherein the conductive film comprises ananisotropic conductive film and the first substrate includes one or moreterminals and one or more devices providing a signal adapted fortransmission along the optical signal path.
 16. The electronic packageof claim 15, wherein the anisotropic conductive film contains aplurality of conductive particles which form a conductive path when theanisotropic conductive film is compressed between the first terminal andthe second terminal.
 17. The electronic package of claim 16, wherein thefirst substrate comprises a die.
 18. The electronic package of claim 17,wherein the die comprises a processor.
 19. The electronic package ofclaim 16, wherein the second substrate includes one or more electricalinterconnects and one or more optical paths aligned with the opticalelement.
 20. The electronic package of claim 18, wherein the anisotropicconductive film comprises an adhesive, anisotropic conductive film. 21.The electronic package of claim 19, wherein the one or more opticallytransmissive units comprises an optical via.
 22. The electronic packageof claim 21, wherein the optical via is formed from an optical polymer.23. The electronic package of claim 14, wherein at least one of the oneor more optically transmissive units transmits a clock signal.